A protective helmet has a jet helmet part and a chin part which are releasably connected to each other by a coupling part. The chin part and the jet helmet part can be swiveled relative to each other by a swiveling mechanism between an integral helmet position and a jet helmet position. The coupling part includes a coupling element on the chin part and a second coupling element on the jet helmet part, which coupling elements engage to form a mutually releasable form-fit coupling. The swiveling mechanism actuates a locking mechanism where the locking mechanism includes a blocking slider and is designed such that, in the integral helmet position, the blocking slider blocks the first coupling element such that a decoupling of the coupling elements is prevented, and in the jet helmet position, the blocking of the first coupling element is released thereby enabling the coupling elements to be decoupled.